2015 TDI battery drain

[compound problems]

I have a 2015 Golf TDI 6 SPD manual. I owned it now for almost 5 years. Every winter when it's below freezing my battery will go dead if it's parked for 2 days or so. One winter I was having a check engine light for the exhaust flap low voltage. This winter it started throwing a code for DEF temp sensor (I don't have the fault code number). I'm suspicious the DEF heater is running when it's parked and killing the battery. I finally just got a battery maintainer and my code for the DEF temp went away.
I data logged the DEF temp and it seemed right. Same as ambient temp and then warmed as I drove.
Has anyone else had these issues?

 

[super1]

I have a 2015 Golf TDI 6 SPD manual. I owned it now for almost 5 years. Every winter when it's below freezing my battery will go dead if it's parked for 2 days or so. One winter I was having a check engine light for the exhaust flap low voltage. This winter it started throwing a code for DEF temp sensor (I don't have the fault code number). I'm suspicious the DEF heater is running when it's parked and killing the battery. I finally just got a battery maintainer and my code for the DEF temp went away.
I data logged the DEF temp and it seemed right. Same as ambient temp and then warmed as I drove.
Has anyone else had these issues?

Have you had the battery tested ?

 

[compound problems]

I replaced the battery 4 years ago approximately. The old one was junk. (I believe from being drained so low so many times) No, I didn't test the new one. The problem continued with the new battery. When the temperature stays above freezing I can leave it parked for a week no problem. It's just when it's colder that it's an issue.

 

[super1]

I replaced the battery 4 years ago approximately. The old one was junk. (I believe from being drained so low so many times) No, I didn't test the new one. The problem continued with the new battery. When the temperature stays above freezing I can leave it parked for a week no problem. It's just when it's colder that it's an issue.

I would get the new one tested

 

[ZippyNH]

Anything plugged in? Have known people to complain then realize a dashcam that's plugged in all the time me or a Android radio is plugged to n and staying "on".
Sometimes easy to overlook small drains that can add up. Even a USB charger that's plugged in...some are vampires

 

[compound problems]

Anything plugged in? Have known people to complain then realize a dashcam that's plugged in all the time me or a Android radio is plugged to n and staying "on".
Sometimes easy to overlook small drains that can add up. Even a USB charger that's plugged in...some are vampires

Nothing plugged in, the cigarette plugs turn off with the key. No dash cam, factory stereo.

I would get the new one tested

I can get it tested, but in my mind at least there is no way that's the problem. Like I meantioned this is a COLD WEATHER ONLY problem. I've had this battery for 4+ years and every winter I have the battery drain issue. If the battery was the problem it wouldn't clear up when the weather gets warmer. Also colder is worse. If it's close to 0° F it'll be too dead to crank just sitting overnight. As soon as it's above freezing temperature it can sit for a week no problem.

 

[ZippyNH]

Dumb question...
Are you leaving your keys in the car or very close to the car? This would easily explain it. Known people that do it cause they park in a garage....
Basically the car never really goes FULLY asleep cause it is reading key present.

Secondly a "new" battery that's older than 3 years is typically junk....

 

[super1]

Nothing plugged in, the cigarette plugs turn off with the key. No dash cam, factory stereo.



I can get it tested, but in my mind at least there is no way that's the problem. Like I meantioned this is a COLD WEATHER ONLY problem. I've had this battery for 4+ years and every winter I have the battery drain issue. If the battery was the problem it wouldn't clear up when the weather gets warmer. Also colder is worse. If it's close to 0° F it'll be too dead to crank just sitting overnight. As soon as it's above freezing temperature it can sit for a week no problem.

One of the worst enemies that puts a strain on a battery is cold weather, & yes what ZippyNH said older than 3 years on your battery is typically junk, it's past its prime

 

[compound problems]

Dumb question...
Are you leaving your keys in the car or very close to the car? This would easily explain it. Known people that do it cause they park in a garage....
Basically the car never really goes FULLY asleep cause it is reading key present.

Secondly a "new" battery that's older than 3 years is typically junk....

Yes I always leave my keys in my car. I park it in my unheated shop. Now the question is is it trying to keep something warm because the keys are in it (surely I'll drive it soon if the keys are there) or is the cold just killing my battery?
They are predicting cold weather this coming week (high of 25°F) I'll pull the keys and park it outside

 

[ZippyNH]

Yes I always leave my keys in my car. I park it in my unheated shop. Now the question is is it trying to keep something warm because the keys are in it (surely I'll drive it soon if the keys are there) or is the cold just killing my battery?
They are predicting cold weather this coming week (high of 25°F) I'll pull the keys and park it outside

Winner winner chicken dinner!!
Take the keys out.
Problem solved.
Most every modern cars with pushbutton start will die in two-3 days if you leave the keys in them.
Honestly the battery might be junk from getting drained daily, but know you know why/how the battery is going dead.
Glad it was something simple
Simple explanation is when your car sees the key fob it's kinda waiting for you to push the start button and does FULLY go to sleep... relays are kept energized, etc.
Google it...it's actually a common issue or was when pushbutton start came out.

 

[ZippyNH]

From Google...


While leaving a key fob inside your car overnight can slightly drain the car battery due to its constant communication with the vehicle, it's generally not enough to completely kill a healthy battery on its own; however, if your car battery is already weak or old, the added drain from the key fob could be enough to cause it to die overnight.
Key points to remember:
Minimal drain:
Modern key fobs are designed to use minimal power when searching for a car signal, so the drain from just leaving it inside is usually negligible.
Battery health matters:
If your car battery is already old or nearing the end of its life, even a small drain like a key fob can be enough to cause it to die overnight.
Other factors:
Leaving other accessories on in the car, like lights or the radio, can significantly contribute to battery drain, even more so than a key fob.
What to do:
Store the key fob away:
If you're concerned about potential drain, consider storing your key fob away from the car overnight, either in a dedicated storage spot or a Faraday pouch that blocks the signal.
Check battery health:
If you suspect your car battery is the issue, have it tested at a mechanic to determine its condition.

 

[GBaugh]

VW has issued a TSB: 27-15-03, Battery Discharged, Diagnosis for Excessive Static Current Draw, release date 7-13-23 for all models except Routan,. With the vehicle in sleep state for two hours, specification is nominal sleep current < 40mA. Sleep state is achieved with all doors, trunk, hood latch closed and vehicle locked to arm anti-theft sys. The TSB doesn't identify any specific load culprits but is more about the method used to test for parasitic load. They want to test for voltage drop across fuses rather than traditional method of pulling fuses because pulling fuses can wake up the control modules. If you suspect the DEF heater, you should be able to pull that fuse overnight as a test. Trunk and glovebox lamps can be hidden cuprits. Alternator field coil can also be a source of drain. You can unplug harness from alternator and see if problem disappears. If it were me, I would install my multimeter in series at the battery and measure the current draw. This parasitic draw test, to be done properly, must be done with a knife switch to put the sys in sleep state. If you don't use the knife switch to switch your am meter into series with batt connection, you will interrupt the batt cable connection which will prevent sys from going into sleep state. If you have an inductive amp clamp, that can be an easier way to perform parasitic draw test.

Regarding storing keyfobs inside vehicle, my understanding is that when the vehicle is locked and armed, the vehicle radio receivers stop looking for input from the two antennas inside the cabin and are only looking for radio input from the exterior proximity antennas in the door handles and luggage compartment so leaving a keyfob inside should not inhibit sleep mode as long as security is armed/locked. Once you unlock/unarm, and open the door, then the cabin radio receivers start looking for presence of key fob inside the cabin. I have a spare key fob hidden inside my cabin and have hever had issues with battery drain. To prove this, I just attempted to open my locked Passat WITHOUT a keyfob in my pocket, but with the keyfob locked inside the vehicle and the doors would not unlock from outside. The sys remained asleep and would not unlock because the control module was not looking for input from the internal cabin antenna.

 

[compound problems]

From Google...


While leaving a key fob inside your car overnight can slightly drain the car battery due to its constant communication with the vehicle, it's generally not enough to completely kill a healthy battery on its own; however, if your car battery is already weak or old, the added drain from the key fob could be enough to cause it to die overnight.
Key points to remember:
Minimal drain:
Modern key fobs are designed to use minimal power when searching for a car signal, so the drain from just leaving it inside is usually negligible.
Battery health matters:
If your car battery is already old or nearing the end of its life, even a small drain like a key fob can be enough to cause it to die overnight.
Other factors:
Leaving other accessories on in the car, like lights or the radio, can significantly contribute to battery drain, even more so than a key fob.
What to do:
Store the key fob away:
If you're concerned about potential drain, consider storing your key fob away from the car overnight, either in a dedicated storage spot or a Faraday pouch that blocks the signal.
Check battery health:
If you suspect your car battery is the issue, have it tested at a mechanic to determine its condition.

We'll find out this week, but I really dont think the key is the problem. It's fine in warm weather, It's been fine the last 4 summers. I did nothing different during the warm weather.

 

[compound problems]

Little update. Weather warmed up and the issue vanished again, so still no conclusion.

 

[super1]

Little update. Weather warmed up and the issue vanished again, so still no conclusion.

I still think you have a bad battery
The battery isn’t under as much stress during warmer weather when starting your motor

 

[compound problems]

I still think you have a bad battery
The battery isn’t under as much stress during warmer weather when starting your motor

I really doubt that. It acted the same every winter for the last 4. Also in the past few months it developed an extended crank issue so it'll crank for a full 2 or 3 seconds before starting. In the winter if it had enough power to crank over it always started, most times it wouldn't even crank at all.

 

[pedroYUL]

If you trust your battery, then it's time to rebuild the starter. Get in touch with @Mozambiquer , he has all of that for a very good price.

 

[compound problems]

Starter is fine. It's a fuel issue. Cranks plenty fast enough.

 

[pedroYUL]

Have you changed your CPS?

 

[super1]

Starter is fine. It's a fuel issue. Cranks plenty fast enough.

Your thread says battery drain make a new thread with the headline fuel issue or extended crime time plenty of threads about that

 

[Mozambiquer]

I replaced the battery 4 years ago approximately. The old one was junk. (I believe from being drained so low so many times) No, I didn't test the new one. The problem continued with the new battery. When the temperature stays above freezing I can leave it parked for a week no problem. It's just when it's colder that it's an issue.

Get the battery tested. And on the 2015 Golf it needs an AGM battery and needs the bem recoded or you'll have short battery life.

 

[Nuje]

I really doubt that. It acted the same every winter for the last 4. Also in the past few months it developed an extended crank issue so it'll crank for a full 2 or 3 seconds before starting. In the winter if it had enough power to crank over it always started, most times it wouldn't even crank at all.

The problem and solution was posted previously.
Leaving the keys in your car drains the battery. In cold winter weather, the drained battery coupled with reduced battery capacity due to cold, makes it difficult if not impossible to start your car.

In the warmer months, the battery's reserve capacity stays much higher, so it's still able to start even with the trickle drain from the BCM not sleeping (it's reading that there's a key available to start the car so is "ready").
In the summertime, if you were to leave the car unused, with the key in it, for a couple weeks instead of just a couple days, I'd guess that you still wouldn't be able to start it.

Bring the key into the house with you, or hang it on the wall of the garage - at least give that a try and see what happens.

 

[compound problems]

Ok, seriously guys. I'm not starting a new thread on the starting issue. I just mentioned that to say that my battery is plenty strong in the summer. The battery drain issue is ONLY a problem when below freezing 32 F, 0 C. It will go dead almost overnight if it is 25 degrees F but can sit for a week if it is above 35. You're trying to tell me that it drains from having the key in it, I don't believe it, there would be a lot more people with the problem with Volkswagen. At this point it's not a big deal anymore, I can use my battery tender in the middle of winter for a month. If someone wants to lend me a commercial freezer and another car for a few weeks I'll test pulling the key in the cold and see if it makes a difference. I'm from Pennsylvania and pulling the key for a few nights won't prove anything cause it hardly stays cold enough. It only has the issue maybe 5 times a winter.
All that being said I did not program the BCM for the new battery so there is a possibility that's the problem. I also had replaced the BCM prior to the battery issue but I had been parking in a heated garage and it only became a problem when I began parking outside.

 

[ZippyNH]

The problem and solution was posted previously.
Leaving the keys in your car drains the battery. In cold winter weather, the drained battery coupled with reduced battery capacity due to cold, makes it difficult if not impossible to start your car.

In the warmer months, the battery's reserve capacity stays much higher, so it's still able to start even with the trickle drain from the BCM not sleeping (it's reading that there's a key available to start the car so is "ready").
In the summertime, if you were to leave the car unused, with the key in it, for a couple weeks instead of just a couple days, I'd guess that you still wouldn't be able to start it.

Bring the key into the house with you, or hang it on the wall of the garage - at least give that a try and see what happens.

Exactly the point I was trying to make...
Seen it on other makes..... BMW/MINI.
SAME SYMPTOMS.

 

[Cuzoe]

I think it's also worth noting that the result of @GBaugh's test doesn't indicate the problem is anything other than leaving the key in the car. Unless I missed something OP is not locking their car. They're just leaving the key in it.

On the other hand if you have your spare key in the car (detected) and then you leave the car but lock it (with your other key) it would be ridiculously poor design by VW if anybody could just walk up and unlock the car. Even non KESSY vehicles can have profiles tied to a given key so the car is aware of which key is used (or present in the case of KESSY).

In that situation the car would go to sleep and would experience none of the battery drain.

 

[Nuje]

My experience with the KESSY implemented by VW is that if a key is in the car and you try to lock it from outside with a second key or have one in your pocket when you tap the door handle dimple, it does indeed lock. And presumably the BCM then goes to "sleep".

If you try to touch that door-handle dimple to lock the car while the key is inside and you do not have a second key on you, it will not lock; and keep everything "awake" ready for you to hit the start button and start the car.

In response to @compound problems: I'm guessing this isn't a widely reported issue because very few people leave their key inside their unlocked car - garaged or not.

Growing up in small-town rural Saskatchewan in the 1980s with cars kept in the garage, my parents wouldn't leave their keys in the car - not because one might get stolen (as proof: in -30°C weather, probably a third of the town WOULD leave keys not only in the car, but in the ignition..., with the CAR RUNNING while they went in and did their grocery shopping or had coffee with the neighbours because you didn't want to get back into a freezing cold car....or maybe your car wouldn't start because it was so freakin' cold out)....but just because....you don't leave keys in the car overnight (?). Or your house keys or key to the liquor cabinet or whatever are on the same key chain?

But you do you; keep saying "can't be that" and looking for another answer without believing or testing the hypothesis supported by knowledge and experience here.